Although horizontal gene transfer (HGT) is a widely accepted force in the evolution of prokaryotic genomes, its role in the evolution of eukaryotic genomes remains hotly debated. Some bdelloid rotifers that are resistant to extreme desiccation and radiation undergo a very high level of HGT, whereas in another desiccation-resistant invertebrate, the tardigrade, the pattern does not exist. Overall, the DNA double-strand breaks (DSBs) induced by prolonged desiccation have been postulated to open a gateway to the nuclear genome for exogenous DNA integration and thus to facilitate the HGT process, thereby enhancing the rate of endosymbiotic DNA transfer (EDT). We first surveyed the abundance of nuclear mitochondrial DNAs (NUMTs) and nuclear plastid DNAs (NUPTs) in five eukaryotes that are highly resistant to desiccation: the bdelloid rotifers Adineta vaga and Adineta ricciae, the tardigrade Ramazzottius varieornatus, and the resurrection plants Dorcoceras hygrometricum and Selaginella tamariscina. Excessive NUMTs or NUPTs were not detected. Furthermore, we compared 24 groups of desiccation-tolerant organisms with their relatively less desiccation-tolerant relatives but did not find a significant difference in NUMT/NUPT contents. Desiccation may induce DSBs, but it is unlikely to dramatically increase the frequency of exogenous sequence integration in most eukaryotes. The capture of exogenous DNA sequences is possible only when DSBs are repaired through a subtype of non-homologous end joining, named alternative end joining (alt-EJ). Due to the deleterious effects of the resulting insertion mutations, alt-EJ is less frequently initiated than other mechanisms.

中文翻译：

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干燥并不能大大增加外源DNA进入核基因组的可及性：内共生DNA转移频率的证据。

尽管水平基因转移（HGT）是原核生物基因组进化中广泛接受的力量，但其在真核生物基因组进化中的作用仍然引起人们激烈的争论。一些对极端干燥和辐射有抵抗力的轮虫类轮虫经历了很高水平的HGT，而在另一种抗干燥性的无脊椎动物中，节肢动物不存在这种模式。总体而言，推测由长时间干燥引起的DNA双链断裂（DSB）可以为外源DNA整合打开通往核基因组的通道，从而促进HGT过程，从而提高内共生DNA转移（EDT）的速率。我们首先调查了五种高度抗干燥的真核生物中核线粒体DNA（NUMT）和核质体DNA（NUPT）的丰度：轮生的轮虫Adineta vaga和Adineta ricciae，缓坡的Ramazzottius varieornatus以及复活的植物Dorcoceras hygrometricum和卷柏卷柏（Slaginella tamariscina）。未检测到过多的NUMT或NUPT。此外，我们比较了24组耐旱生物体及其相对较少的耐旱亲戚，但在NUMT / NUPT含量上没有发现显着差异。干燥可能诱导DSB，但是在大多数真核生物中，不可能显着增加外源序列整合的频率。仅当通过非同源末端连接的一种亚型（称为替代末端连接（alt-EJ））修复DSB时，才能捕获外源DNA序列。由于产生的插入突变的有害影响，alt-EJ的启动频率低于其他机制。